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1.1'' 



3 :L. 






Portland Branch Llbrar. 
U. S, 'ij^l^ of Agriculture 
ACE--182 




"^^-« 



APPLE STORAGE IN THE YffiNATCHEE-OKAI^IOGAN VALLEY 



by 



W. V. ^Hukill, Senior Agricultural Engineer 
Bureau of Agricultural Cheiiiistry and Engineering 

and 

Edv\fin Smith, Senior Horticulturist 
Bureau of Plant Industry 

Agricultural Research Administration 
UiaiED STATES DEPARTMENT OF AGRICULTURE 

August 1942 






■^^J^- 



FOREITORD 

Among the underlying factors affecting the economic position of 
the fruit industry in the Yfenatchee-Okanogan area, the condition 
of fruit products as the consumer receives them has been recognized 
as one of primary importance and one that has not been given suffi- 
cient attention in the past^ It is obvious that a fresh fruit 
industry cannot remain stable if its products do not reach the con- 
sumers in a fresh and appetizing condition - one that gives satis- 
faction and stimulates continued demands The factor of condition 
is particularly significant with the fruit industry of this area where 
the reputation of its product is so largely reflected by the consumer 
estimation of a single apple variety - the Delicious. 

If not given proper attention in all phases of harvestings packings 
storing, and distributing, the Delicious apple is especially liable 
to be in an overripe and unpalatable condition when it reaches the 
consumer. Apples from this area are too frequently in this condition. 

Consideration of this situt^tion caused the Secretary of Agriculture 
to direct the Bureau of Agricultural Chemistry and Engineering and 
the Bureau of Plant Industry to investigate the handling and storage 
of apples in this area. In this preliminary report are included 
some of the results of this study and recomiTiendations by the investi- 
gators. Special attention of growers, shippers and warehousemen at 
this time is directed to the sections on storage management and 
operation in view of the present difficulty in making plant altera- 
tions or extensions. 




b y /^J^/X>k < J(A.^^}^ A ^ 



George T. Hudson 

Special Representative 

US Department of Agriculture 



^CE--182 



APPLE STORAGE IN THE TffiN AT C HE E- OKANOGAN V/J.LEY 

lU V. Hukill, Senior Agricultural Engineer 

Bureau of Agricultural Cheniistry and Engineering 

and 
Edwin Smith, Senior Horticulturist, Bureau of Plant Industry- 
Agricultural Research Administration 

CONTEN^S_, 

Storage Capacity 
Effects of Cold Storage 

Character of Fruit 

Respiration 

Ripening Process 

Freezing Temperatures 
Factors Affecting Storage Quality of Apples 
Storage Disorders 

Relation of Facilities to Fruit Condition 
Refrigeration 

i^rinciples of Heat Removal 

Three Steps in the Refrigerating Process 

Three Parts of a Refrigerating System 

Condensox', Compressor, Evaporator 

Cold Storage Rooms 
Sources of Heat 

Field Heat 

Heat of Respiration 

Incidental Heat Sources 

Air Infiltration 

Heat passing Through Insulation 
Prccooling 
Storage Period 
Storage Design 
Management 

Reducing Initial Fruit Temperature 

Segregation of Long Storage Apples 

Segregating to Avoid Soft Scald 
plant Operation 

Core Temperature 

Ammonia Pressures 

Stacking Boxes 

Air Circulation 

Frosted Coils 

Brine Treatment 

Care of Condenser and Compressor 

Controls 

Fans and Ducts 

Keeping Equipment Balanced 

Appendix 



STORAGE CAPACITIES 

In the spring of 1941 a survey was made of the cold storages in the 
Vfenatohee-Okanogan area. The results were covered in a mimeographed 
report issued "by the Bureaus of Agricultural Chemistry and Engineer- 
ing, and Plant Industry which indicated the approximate number of 
boxes that could be -held in cold storage in the. area and the approxi- 
mate rate at v/hich boxes could be cooled during harvest. By September 
1941 some additional capacity had been provided. ..>. ■ 

Table I shows the cold storage space for the area as of September 1941, 
together with the approximate number of boxes of apples packed in 1941- 
in each district. This does not include the pear crop. 

Table I. .■ ^ ■ ■ ■. . ' 

COLD STORAGE SPACE III TliE T-TiLIATCHEE-OKAIIOGAlv' AREA 

IK ^ . ■ ; . . , . \ 

SEPTEI.IBER 1941 ' . ' " ' - ' . " .' -" 

District 



Oroville-Ellisford-Tonasket 

Omak-Okanogan-Malott 

Brews ter-Pateros 

Chelan-Chelan Falls-Azwell 

Entiat 

Wenatchee-Orondo 

Monitor-Cashmere-Dryden 

Pes has tin- Leavenworth ; 

Total 

About 53 percent of the 1941 crop was of the Delicious varioty-- 
Common and Reds. The percentage varied in the districts from about 
40 percent in '.Yenatchee to about 70 percent in Brewster-Pateros. 
In any one district the period of Delicious harvest is relatively 
short, which means that apples are brought into cold storage at a 
high rate for a short time. The Delicious crop for 1941 and its re- 
lation to the daily cooling capacity of the cold storage plants are 
shovm in Table II. ' . " " 

EFFECTS OF COLD STORi'-X-E • . * 

CHARACTER OF FRUIT 

The need for refrigeration in storing any product arises from the 
nature of the product. Fresh fruits and vegetables are alive for 
a time after they ar^ harv<jstcd. The length of time they may be 
preserved for consumption depends upon how quickly the end of. life 
approaches. Generally, the changes taking place are sloy\red down by 
low termperatures. Each kind of product and each variety has its 
own characteristics v\rhich determine how long and under vj-hat con- 
ditions its storage life may be extended. There arc differences 
within each variety which depend upon such things as soil conditions, 
climate, etc., but by close study of individual varieties fairly 



Cold Sto 


rage Space 


1941 Crop . 
Packed Apple 


Cars 


Boxes 


Boxes 


757 


605,000 


1,326,0^0 


836 


669,000 


1,440,000 


820 


655,000 


1,239, #00 


1,604 


1,280,000 


2,099,000 , 


442 


353, too 


922,000' 


3,185 


2,540,000 


2,186,000 , . 


1,412 


1,130,000 


2,059,000 ■ 


813 . 


650,000 


661,000 


9,869 


7, 882, too 


11,942,000 



2. 



Tabic II. 

KEIATION OF COOLDIG* CAPACITY OF COLD STOMGE FU^TS 

TO 
FJiiBER OF BOXES OF DELICIOUS iirVLSS IN 1941 CROP 



District 



1941 Daily Days Amount 

Delicious Cooling Required Cooled 

Pack Capacity To Cool In 15- 

All 



ijoxcs 



Boxc s 



Orovillc ) 
Ellisford) 
Tonr.slcct ) 



Oiaak 

Ok--'.nogan 
Llalott 

Brcv;stcr 
pa'toros 

ChJlan ■ 
Azvoll 
Mans on 

Entiat 



Tiicnatcht.c ) 
Orondo ) 

Monitor ) 
Cashmere ) 
Dryden ) 

Pcshastin ) 
Leavenworth) 



896,000 32,000 

604,000 28,800 

876,000 25,000 

1,26-6,000 43,500 

450,000 19,700 

892,000 94,000 

■ 907,000 47,800 

391,000 17,000 



Viienatchee-) 

Okanogan ) 6,292,000 298.600 

Area ) 

7880 cars 374 cars 



Delicious 

Days 

41 

21 

34 

29 

23 

9.5 

19 
23 

21 



♦Cooling from 65° F. to 32° in 7 days. 



Days 



Boxes 



Excess not 
Cooled in 
15 Days 



Boxes 



330,000 566,000 



432,000 
387,000 



172,000 
489,000 



652,000 614,000 

296,000 164,000 
1,410,000 -518,000 



717,000 
255,000 



190,000 
136,000 



4,479,000 1,813,000 
5610 cars 2270 c-rs 



accurate generalizations can be made by which the storage reactions 
may be predicted. The rate of ripening in applies and pears speeds 
up markedly as soon as the fi*uit is removed from the tree, provided 
there is no lowering of temperature. VJlicn picked at optimum maturity 
and delayed in refrigeration, the effects on the fruit of this rapid 



3. 

ripening are not apparent at the time, but v/ill be reflected in a 
shortened, life of the fruit, possibly to be observed after several 
months in cold storage. 

RESPIRATION 

As apples or pears ripen, heat is produced. At 32° F. there is suf- 
ficient ripening in a carload of apples to emit enough heat to melt 
about 100 pounds of ice in 24 hours; at 40° the amount of heat is 
twice as great; at 60° the heat of respiration would melt about .78'5 
pounds of ice in this time. In cooling Delicious apples from 70*^ 
to 35° in six daysj the amount of heat generated through ripening is 
almost one-third of the sensible or field heat. If cooled in three 
days, only about half of this amount of heat of respiration has to be 
dealt with; but if cooling takes two weeks, the amount is doubled. 
On account of the heat of respiration, it is necessary to remove heat 
from apples in cold storage continuously. For this reason, apples at 
the center of a block may have a tomper.'Ature several degrees higher 
than those near the aisle unless provision hC'S been made for the cold 
air to circulate about the packages. ' . - ' ' " ■ 

RIPENING PROCESSES /' • -'^ :-._ f 

l^Jlicn an apple is picked it ho.s a capacity for continuing to live. 
As it ripens, this capacity is used up, and the rate at vAich it is 
used up determines hovf long the fruit v/ill be usable. Ripening has 
been found to proceed about in proportion to the rate at which respi- 
ration takes place. At lov/ temperature the rate of ripening, or of 
using up the potential life of the apple, is much slower than at 
higher temperatures. Thu rate of ripening is at a minimum at tempera- 
tures just above the freezing point. 

FREEZING TElJlFEaiTURES ■■'■■ '' '■' - -•- 



Different varieties of fall and winter pears freeze at temperatures 
ranging from 26.4° F. to 28.8° v;ith an average freezing point of 



o 



rO 



7.7 . Freezing temperatures for fall and v.-inter varieties of apples 
range from 27.8° to 29.4° with an average of 28.5°. To permit, a mar- 
gin of safety against freezing, storage temperatures of 5?> to 31 are 
usually recommended for apples, with slightly lower temperatures for 
pears, pears may be precooled dovm. to 23°, 

FACTORS AFFECTING STORAGE QUALITY OF i^PPLES 

It is a' common experience to have apples of a given variety keep bettor 
in storage when groivn in one locality than when gro-'mi in another. Cli- 
matic, soil, and tree condition have a direct influence on storage 
response. Conditions under which a fruit is harvested and packed also 
are most important. 

GROWING CONDITIONS 

Apples produced under conditions v;hich result in normal growth and 
maturity of tree and fruit usually have the best storage quality. 
It is recognized that where an apple tree makes an abnonnal growth 



4. 

with heavy foliage and is late in maturing its woodj as happens in 
young orchards or in orchards having abnormal supplies of nitrogen 
and water, the fruit usually is abnormal in size, texture, and 
quality. This frequently happens when a tree bears a light crop. • 
After a certain period in the summer, increased size in an apple 
fruit is more related to growth in size of cells than it is to an 
increase in the number of cells. Large apples consist of large cells, 
and small apples consist of small cells with relatively thicker, 
stronger cell walls. This accounts for the firmer texture in the 
smaller-sized fruits and for the better storage qualities in fruit 
grovm under conditions contributing thereto. 

As apples are received for storage, it is important to keep the 
identity of those lots coming from trees or orchards where growing 
conditions are likely to cause poor storage quality so that they iiiay 
be disposed of promptly.^ 

HAWESTIMG COITDITIQNS 

The maturity of apples at harvest has a direct influence on the 
fruit's keeping quality. Vvhen picked before becoming adequately 
mature or after reaching an advanced stage of maturity, the fruit 
may be susceptible to storage disorders that might be avoided if 
harvesting were done at an optimum stage of maturity (see storage 
disorders). Blue mold decay (Penicillium expansum) is the most 
serious storage rot in the Pacific Northwest. This is a fungus that 
most commonly enters apples and pears through injuries. These in- 
juries may take place during picking, hauling, Washington, or pack- 
ing. The causes of the larger injuries are obvious and may be detected 
and corrected by an observant operator. Spores of fungi are micro- 
scopic and can germinate and grow in injuries not seen by the naked eye. 
For this reason it is important to avoid as much as possible all small 
bruises because where pressure has been sufficient to cause a small 
bruise, it possibly has been great enough to cause a microscopic in- 
jury in the skin. 

Pressure against the side or bottom of an old orchard box is particu- 
larly hazardous, because this may result in pressing spores of rot- 
producing fungi into minute injuries. Old orchard boxes carry great 
quantities of spores and, unless sterilized before use, are considered 
a prime source of infection. 

The washing process, if not done carefully, frequently contributes to 
increased decay and shriveling in fruit during storage. V/hcn the wash- 
ing process is sufficiently severe to result in visual injuries, micro- 
scopic injuries also probably abound. Aside from a reduction in the 
washing solution temperature, the use of an abundance of clean rinse 
water is an important means of preventing washing injuries. 

Fewer washing injuries occur v/ith a given washing solution temperature 
after apples arc allowed to remain in cold storage for several weeks 
after harvest. There are no added risks when apples are washed after 
being held at 32° F. for several weeks. This is not true where the 
fruit is held until it becomes ripu. 



The vmshing process may b'^ sufficiently severe to cr.us^ skin injuries 
without seriously affecting the rate of ripening in storage. However, 
such severe treatments so affect the skin that increased moisture 
losses and shriveling take place and fruit thus virashcd is not suitable 
for long-time storage. . .- ... 

The washing, grading, and packing equipment may be the cause of mechani- 
cal injuries and should be given a careful inspection periodically to 
detect faults that may be responsible for unnecessary skin punctures 
or bruises. 

STORAGE LIFE OF DELICIOU S 

Over half the apples frora the 'vVenatchee-Okanogan area arc of the Deli- 
cious variety. To reach the markets in first class condition, this 
variety has been found to require prompt cooling and low temperature 
storage. The storage life of Delicious is directly related to the 
temperature at "#hich the fruit is kept. There is no indication that 
temperature fluctuations in themselves have any effect on storage life. 
That is, it is the level of temperature and the time of cxposuri_ to 
each temperature level that fixes the storage life and abrupt changes 
in temperature do not shorten the life of the fruit. One exception to 
this rule is in the incidence of soft scald 'vvhich under some conditions 
is induced by sudden cooling to 32*^. The accompanying chart (Fig. 1) 
shows the expected period of storage for Delicious under different 
temperature conditions. Higher temperatures than those indicated should 
be allowed for during transportation and distribution v/hen considering 
storage at the point of origin. The upper section illustrates the 
effect of continuous exposure to various temperatures, while the lower 
section illustrates the effect of a few typic; 1 cooling rates. In each 
case it is assumed that, exposure to the condition indicated starts im- 
mediately after picking. The normal life expectancy of Delicious apples 
as shovra on the chart applies v/hen the fruit is groi-vn on mature, healthy 
trees, has not been injured in any way, has been picked at the right 
stage of maturity and is handled and stored under sanitary conditions. 
Some conditions of growth may result in abnormal fruit which is sus- 
ceptible to invasion by rot-producing fungi. Usually this may be de- 
termined only by the history of the fruit from a given orchard. Fruit 
from such orchards may not be expected to have a normal storage life. 

IThen Delicious or red strains of Delicious (Starking, Richared, etc.) 
are picked before becoming adequately mature, they may bo susceptible 
to storage scald to such an extent that their commercial storage life 
may be cut in half, VJlion picked at an advanced stage of maturity or 
after watercore has made its appearance, the fruit may become stale 
in flavor and mealy or develop internal breakdovm long before the indi- 
cated dates. Although this V':riety is very responsive to proper hand- 
ling, it cannot be considered a late keeper. Under the best of storage 
conditions, it begins to lose its full varietal flavor after January. 
Although it may be kept crisp and juicy until the spring months, its 
flavor usually is mild or neutral by late vj-inter when it quickly be- 
comes mealy and stale aft^ r being taken to living-room conditions. A 
delay of a week or ten days in the orchard virill often decrease the life 
of the fruit two or three months. Ko storage treatment can restore that 
part of the fruit's life which has been spent. 



6. 



Figure 1 

■ ■ mmL^L STORAGE LIFE EXPETAIjCY 

DELICIOUS APPLES 

FOR CONTIGUOUS STORAGE 

AT 70° 

xxxxxx 

AT 60° 
XSXXXXXXX 

AT 50° 

AT 40° 

AT 36° 

AT 32° 

AT 30° 

' OCTOBER ' HOVEIvBER' DECEIvBER' JAITUARY ' FEBRUARY' MARCH ' APRIL ' MY ' JUHE 



FOR Various r..tes of coolilig 

COOLED TO 30° IF 7 D^YS , 

jjjim 1 

COOLED TO 32° m 7 DaYS ' . ' 

i^RIL 5 
COOLED TO 360 jw 7 DaYS; THEl TO 32° HI 4 TffiEKS 

I'lARCH 20 
COOLED TO 40° IN 7 D..YS; TIffiK TO 21 D.-.YS ..T 40°; THEN TO 52° IN 28 I-DRE D.vYS 

FEBRUxJiY 10 



COOLED TO 360 jjj 7 jj^^yS 
XXXXXXXXXXjCQGvXXj IXXXXXXXXXXXI w i-iyCXX 

J^J^UiJlY 15 

COOLED TO 36° JIT 6 VJEEKS 
XXXXX]vXXXXXXXXXXaXXX:QDCOQCX 
DECELffiER 20 



*FOR K.CH YffiEK OF 
EXPOSURE BEFORE 
STOR..GE xvT 70° 
DEDUCT 9 7EEKS OF 
STOR^^GE LIFE; ^.T 
53° DEDUCT 1 MONTH 
OF STOR--^GE LIFE. 



7. 

The storage period covers only one part of the process of handling 
apples from the tree to the consumer. "Cultural conditions, hand- 
ling during harvest, cooling, storing, transporting, distributing, 
and treatment in the hands of the consumers, each influences the 
final quality of the apple. Shortcomings in treatment during any 
phase, from production to consumption, cannot be overcome by ex- 
cellence of treatment during any other phase. After picking, the 
length of life of the fruit depends directly upon the fnuit tempera- 
ture. High temperatures at any time after picking hasten the pro- 
cesses that finally make the apple useless. ITnether they occur in 
the orchard, the warehouse, or a store, the effect depends upon the 
temperature level and duration of expjsurc. Responsibilitj;' for 
temperature control and resultant apple condition is not entirely in 
the hands of the storage operators'. It is only because apples are 
ordinarily in storage longer than they arc in the other processes 
that temperatures in storage have more to do V'^ith final condition 
than those at other times. . , . 

OTHER VARIETIES r ::■■:■ ■:^ ■';.;^.- ' :■ :.'... 

For most apple varieties other than Delicious, similar relations be- 
tv\reen temperatures and storage period v/ill apply. There is a con- 
siderable variation, hovj'ever, among varieties in the length of time 
they will keep at any givL.n temperature. Certain varieites in some 
areas react unfavorably to temperatures below 36° or 40'-*, but for 
the most part. Northwestern apples should be stored at 30° to ,31°. 
One modification of this general rule, as it relate. s to soft scald, 
should be mentioned. A low temperature injury knovvn as "soft scald" 
may be induced by placing susceptible fr.iit v/here air temperatures 
below 36 prevail. Such fruit should not be cooled in air tempera- 
tures b^^low 36°. Jonathan apples are especiallj^ susceptible. Over- 
mature or ripening Rome Beauty, Golden Delicious, and Yifinesaps should 
also receive this consideration. Yfhen the latter varieties are not 
over-mature and are stored imiTiediately after picking, there is little 
danger from precooling or storing at a temperature of 31°. 

- STORAGE DISORDERS 

"Storage scald" or "superficial scald" is quite generally controlled 
vd.th oiled v>rraps, while "soft scald" or "deep scald" is not. The 
latter occurs with certain apples which are exposed to low tempera- 
tures at a certain stage of ripening. "i^Taen apples are held in an 
atmosphere of 35 percent COo g^-S for 24 hours prior to storage, they 
arc made practically immune to soft scald. Soft scald has not been 
reported in common storage. It rarely occurs at 36°, though the life 
of the fruit is materially shortened at this temperature as compared 
to storage at 30° or.31°. 

Bitter pit cannot be controlled in cold storage. Most of the fruits 
that would show the disease if they were allowed to ripen in storage, 
can be sorted out before storage by permitting the fruit to become 
mature on the trees. 

The three most important storage rots in the Northwest are blue mold 
rot, gray mold rot, and perennial canker decay. Contamination of 



apples by' spores of fruit rots takes place largely in the orchard or 
between the orchard and cold storage. The chance of contanTination of 
packed fruit in cold storage is remote. Contamination of frait from 
mold spores carried in the storage air may be reduced somevxhat by 
fumigating the rooms while empty. Sulfur dioxide gas is an effective 
fumigant, and it is produced cheaply by burning sulfur. 

Low temperatures inhibit mold grov.'th. Although the amount of decay 
may be reduced by good storage temperatures when fruit has been con- 
taminated, decay will not be prevented by perfect storage condition. 
It is necessary to institute precautionary measures in the orchard 
and packing shed. These include sareful and prompt handling, good 
picking buckets, clean orchard boxes, frequent cleaning, of washing 
tanks, adequate rinse with un»ontaminatcd water, efficient and sani- 
tary packing equipment, clean packing gloves, and dust reduction in 
the packing house. It is important that fruit bo packed before it 
becomes ripe. 

Skin breaks are the most cominon places for entry of blue mold spores. 
Fruit advanced in maturity v;hen pi«ked is most susceptible to entries 
at lenticels. 

Gray mold contamination generally conies from decaying leaves or other 
vegetation in the orchard, such as alfalfa. Unlike blue mold, it vj-ill 
cpread rapidly from one fruit to another through the wraps unless 
copper impregnated paper, known commercially as the "Hartman Y/rap," 
is used. 

Perennial canker decay, commonly called "bull's eye rot," comes from 
spores originating in cankers on the limbs of apple trees. Sains 
frequently carry the spores from tree to fruit. Fruit should not be 
stacked under infected trees. There is no known control after apples 
become contaminated, but the rot seldom appears before the fruit be- 
comes firm-ripe. Contaminated fruit should be given prompt refrigera- 
tion and placed in consumption while still firm. It is a good rule 
to market such fruit while still classified as "firm." 

Internal breakdovm of various forms occurs in several varieties. 
"Jonathan breakdovm" occurs in fruit picked at an advanced stage of 
maturity. Late pickings should be given prompt refrigeration and dis- 
posed of at an early date. "Core breakdovm" in Delicious frequently 
occurs in water core tissue. Viater core largely disappears in storage, 
but the tissue is weak so that any variety showing much water core at 
harvest should not be held for late storage. 

Shriveling or wilting takes place to a greater extent in some varieties 
than in others. Pears or apples harvested before becoming mature are 
subject to shriveling. Liaturit^/' at pieking is especially important in 
avoiding excessive shriveling in storage with some varieties of pears. 
Removal of wax from the skin by "WB-shing apples and pears in virax solvent 
solutions causes the fruit to be more susceptible to shriveling. 

To prevent shriveling in storage it is important to maintain the rela- 
tive humidity of the storage atmosphere at approximately 85 percent. 
Packing apples in closed containers and with wrappers reduces the 
amount of shriveling but will not prevent it if the relative humidity 



9, 

of the storage air remains below an optiraum range for long periods of 
time. In storages with air circulation systmes the greater the velo- 
city of air passing over the fruit,, the more important becomes the 
necessity of maintaining the relative humidity at 85 percent. 

RELATION OF FACILITIES TO FHJIT CONDITION 

The effect of prompt cooling and proper holding temperature on the 
condition of apples is not necessarily reflected in a premium price 
on well-handled lots. The fact that a lot of fruit handled carelessly 
may sometimes bring a better price than a lot which has. been cooled 
and stored under best conditions, tends .to obscure the real difference 
in condition. Viliether or not improved condition results in an immedi- 
ate price return, there is no question that the demand for apples over 
a season or the general price, levels over a longer period arc based on 
consumer experience with apples from this ar^a. 

Most of the storages in the area handle more Delicious than can be 
cooled promptly. In order to dett-rmine vdiether this overloading has 
an effi^ct on condition, inspection certificates viere examined on ship- 
ments from a- number, of plants as the 1941-42 season progressed. One 
of these plants had cooling capacity sufficient to cool the Delicious 
promptly to 32° F. as fast as they came in, vriiile others located in 
the same district were overloaded at harvest time. All certificates 
from the one house were included in one group, and those representing 
shipments at about the same dates from the other houses wore included 
in another group. These were from storages vj"ith varying degrees of 
overloading. In shipments up to November 1, there was no noticeable 
difference in condition between the tvro groups. On November and Decem- 
ber shipments, certificates from the first group were noticeably 
superior. There were 41 certificates from the one house in January 
and 43 in the other group. All 41 had less than 1 percent decay, and 
there were no notations of any ripe apples. Of the 43, 13 showed 1 
percent or more decay, including 6 having some lots ranging to 8 per- 
cent or more; 10 showed at least a few ripe apples. The difference 
bet¥(feen the groups increased as the season progressed. From late 
February through April 2, 12 certificates were found from the one 
house and 23 examined from the others. In the first group, only one 
showed as much as 1 percent decay, while of the second group, 16 had 
lots with 1 percent or more, including 7 with a "range of decay"!/ 
or some lots removed from the shipment for reconditioning after in- 
spection. .,.-■■ 

This comparison indicates only th'e difference between the groups at 
shipping point. It does not show what the difference may have been 
after the subsequent period of transportation and market handling. 
The plants from which the above "certificates were obtained were not 
in one of the districts having the greatest deficiency in cooling 
capacity. They represented perhaps average degrees of overloading. 
It is obvious that without adequate cooling facilities, the general 
level of fruit condition and consumer satisfaction cannot be expected 
to command maximum returns from the crop. It i-s also clear that for 

1/ "Range of decay" is a term used to describe lots having boxes 
with over 5% decay. 



10. 

the duration of the war, little material will be available for reliev- 
ing the deficiency in cooling capacity. If substantial gains are to 
be made in the condition of fruit delivered from the area, they will 
have to come largely from improved handling and operat-ing practices 
which permit the limited cooling capacity of the area to be used to 
best advantage. 

HEFRIGEaATIQN 

FAIJILIARITY YaXK r ROC ESSES 

The best way to become familiar v/ith refrigeration is to work with it 
and use it. Each cold storage plant has characteristics of its own 
which require familiarity vj-ith that particular plant to permit taking 
advantage of its good points and to avoid difficulties that may not be 
common to other plants, Hovrever, general principles of refrigeration 
apply to all plants, and familiarity with them v/ill enable an operator 
to take better advantage of his experience. These are covered in text 
books, and more specific information such as refrigerant characterist- 
ics, insulation values, fan and duct data, requirements of stored 
products, condenser, compressor, and evaporator characteristics, cool- 
ling surface, power requirements, etc., is given in handbooks. A few 
references are listed in the a.ppendix._ 

PUl^IPING HEAT 



The process of refrigeration might be likened to pumping air out of 
a tank to a pressure lower than that of the atmosphere. Once the de- 
sired low pressure inside the tank is reached, the only additional 
pumping necessary is to remove the air entering the tank by leakage 
and the amount of pumping will depend entirely upon the amount of leak- 
age. 

In the case of a refrigerated space, it is desired to maintain a cer- 
tain temperature belovf that of the surroundings. Heat is pumped out 
until the desired low temperature is reached v/hereupon further pumping 
is necessary only to remove the heat that enters the chamber "by leak- 
age through v/alls and open doors or that v^rhich is generated within the 
space. 

Yftien pumping air from a vacuum tank, if only a slight degree of vacuum 
is required, less poorer is needed; and a smaller pump will suffice than 
where a high vacuum is required. The size of the pump required and 
the horsepower of the motor depend upon tvro factors: (l) the amount of 
air to bo removed and (2) the pressure inside the tank. If too much 
air is allowed to enter the tank, the pump cannot remove it, and the 
desired vacuum cannot be maintained. Similarly in a refrigerating 
system, if only a moderately lov/ temperature is required, less power 
and a smaller compressor are needed than where a very lov.'' temperature 
is des'ircd. Furthermore, if the refrigeration machinery does not have 
the capacity to pump out the heat as fast as it enters the chamber, 
the desired lov;- tcmpei'aturc cannot be maintained. 

In extending the comparison, the factors determining the size of the 
pumps are, in the case of the vacuum, (l) pressures, usually expressed 



11. 

in pounds per square inch, and (2) amount of air, expressed as pounds 
per minute. In the refrigerating system the factors are: (l) Tempera- 
ture expressed in degrees, and (2) amount of heat, comraonly expressed 
as "Btu's." The term, "Btu," (the amount of heat required to raise 
the temperature of 1 pound of water 1° Fahrenheit) corresponds to the 
term "pound" inasmuch as they both'express definite quantities of the 
thing to be handled, 

QUANTITY OF HEAT - •'-'-■■''''■■/"''■/ 

Btu may be an unfamiliar term, but in dealing with refrigeration prob- 
lems, it is just as necessary to consider the quantity of heat to be 
handled as it is to speak of pounds of air or gallons of v,rater w^hen 
computing the necessary sizes of air or wa.ter pumps for given jobs. 
One pound represents a very definite and measurable amount of air, and 
it is still the same amount of air regardless of the pressure under 
which it is placed. Likevv'ise, one Btu represents a definite and meas- 
urable amount of heat, and it remains the same amount' of heat regard- 
less of the existing temperatures. ' .■ ' 

The refrigeration demand upon the machinery frequently is spoken of in 
terms of "tons." This had its origin through -a comparison of refrigera- 
ting capacity, or demand, with the amount of refrigeration secured from 
molting 1 ton of ice. As it requires 144 Btu's of heat to change 1 
pound of ice to Irvator at the melting point, 288,000 Btu's are required 
to melt 1 ton of ice. Yfeere it is necessary to remove 288,000 Btu's 
of heat in 24 hours, 1 ton of refrigeration is required. 

If, in a storage building, a temperature of 32° Fahrenheit, is to be 
maintained, for example, the refrigeration system will have to remove 
an amount of heat just equal to the 'aaount vmich enters the building. 
The heat entering may come from a number of source So In the first 
place, if the outside temperature is above 32", some heat will come 
in through the walls. This amount can be reduced by insulation, but 
no amount of insulation virill exclude all heat leakage. If there are 
cracks in the building, or if doors or windows are open and permit 
warm outside air to enter, a second quantity of heat will be introduced, 
the amount depending upon the temperature and quantity of air. If 
materials having temperatures above 32° are placed in the cooled space, 
they will introduce still another quantity of heat, the amount depend- 
ing on the temperature, the weight, and the nature of the material. If 
the materials are living, as for example, apples, they will produce 
heat continually; and this heat is in addition to that which they con- 
tained vmen first put in the storage. The heat from all of these 
sources and from other incidental sources, combines into a quantity of 
heat Y/hich the refrigerating system must remove. If the system has 
sufficient capacity it can all be pumped out. If the amount of heat 
introduced into or produced within the building exceeds the capacity 
of the refrigeration system, some of it vfill remain in the fruit and 
cannot be taken out until the rate of heat intake into 'the building 
has dropped below the rate at which it can be removed. 

The amount of heat that a refrigeration system can remove may be in- 
creased or decreased by the conditions under vfhich it operates, but it 



12. 

v/ill "be seen that no manipulation of air movement or special stacking 
of boxes or other adjustment can prevent the accumulation of heat if 
it is being introduced faster than it is being removed. 

THREE STEi-S IN THE fiEFRIGEl^TING PROCESS 

Heat, like air, is handled in definite quantities; but, unlike air, it 
cannot be moved bodily from one point to another. By its nature it 
moves from a position of high temperature to one of lovj- .temperature. 
A refrigerating system, or heat pump, must take advantage of the ten- 
dency that heat has to move from high to low temperature. Heat moves 
from the storage room through the cooling coils to the ammonia Y/hich is 
at a lovj-er temperature. The compressor takes this heat and changes it 
to a condition of much higher temperature. (just how this rise in 
temperature level is accomplished need not be considered for the present 
discussion.) The heat is then permitted to move into the condenser cool- 
ing vra.ter, here again taking advantage of its tendency to move from a 
condition of high tempex-ature (the coiiipressed ammonia) to one of lower 
temperature (the cooling water). 

THREE Pi^TS OF REFRIGBR^TIHG SYSTEM 

The above three steps in heat removal are accomplished by the three 
essential parts of the refrigerating system. The heat i.s removed from 
the room by the evaporator either in the form •£ direct expansion pipes 
or coils over which air is blown. It is changed to higher temperature 
heat by the compressor. It is finally discharged to the cooling water 
by the condenser. Since all the heat removed must pass in turn through 
each of these three parts, the capacity of each part needs to be suffi- 
cient to transfer all the heat. 

In the evaporator or cooling coils, the amount of heat picked up de- 
ponds upon (l) the temperature difference between the refrigerant 
(ammonia) in the coils and the air outside the coils, (2) the ajaount 
of coil surface exposed and (o) the resistance to heat flow through 
the pipes. The resistance to passage of heat into the coil in turn 
depends not only upon the cleanness of the coil but also upon the velo- 
city of air past the coil and the velocity, of the refrigerant (whether 
liquid or vcpcr). Accumulated frost mo.y greatly increase the resist- 
ance is increased by an accumulation of frost, or if there is not enough 
piping surface exposed, it will take a large temperature difference be- 
tu-een the inside and outside of the coil to permit sufficient heat to 
pass into the coils. This means a low ammonia temperature. It is the 
TiTork of the compressor to boost the temperature of the o.mmonia to such 
a point that heat will flow from it into the condenser vvater. If, due 
to high resistance or insufficient surface in the cooling coils it is 
necessary to maintain a low ammonia temperature (which means lov.'' suction 
pressure), the compressor is forced to boost the temperature from a low 
point, and it cannot handle as much heat as if the suction temperature 
virere higher. 

The compressor must also discharge the ammonia at such a temperature 
that heat will flow from it to the cooling water in the condenser. In 



13. 

general a compressor «an handle more heat if the temperature in the 
cooling coils is kept as high as possible and the temperature in the 
condenser as low as possible. The same conditions also reduce the 
amount of power used in removing a given amount of heat. 

When the ammonia enters the condenser, heat passes from it into the 
cooling water. As in the evaporating coils the amount of heat passing 
from the ammonia to the cooling water depend? upon (l) the temperature 
difference between the ammonia and the water, (2) the amount of surface 
exposed, and (3) the resistance to heat flow through the condenser pipes. 
Here also, the resistance to passage of heat depends upon the water velo- 
city, the ammonia velocity, and the cleanness of the coil. Scale, which 
tends ts^ collect on the pipes from the cooling water, may increase the 
resistance markedly. If this scale is permitted to build up or if there 
is not sufficient cooling surface, the required quantity of heat can 
only bo transferred to the water oy having a large temperature difference 
betTfeen ammonia and water. As pointed out before, the high ammonia 
temperature means reduced compressor capacity and high power consumption. 
An adequate supply of -water as cold as possible v/ill contribute tov^ard 
a low a.mmonia temperature in the condenser and therefore low power con- 
sumption. 

CONDENSER _ ..• 

The condenser has one purpose. It must permit the passage of heat from 
the compressed ammonia to the cooling water (or air in an atmospheric 
condenser) and do so at as low an ammonia temperature as possible. It 
must pass on all the heat which has been taken up in the evaporator, 
and in addition, the heat which has been added by the work of. the com- 
pressor. The passage of heat into the cooling water is facilitated by 
a large amount of cooling surface, by a large quantity of cooling water, 
by a low water temperature, by a high velocity of v\fater and of ammonia 
past the surface. A high o.mmonia temperature also increases the amount 
of heat transferred to the cooling v/ater, but it is the duty of the con- 
denser to receive and discharge the ammonia at as low a temperature as 
possible. The design of the condenser and its operation should be 'such 
as to remove the required amount of heat without excessive ammonia 
temperatures. _ 

In operation, . the effectiveness of the condenser may be judged by the 
head pressure indicated on the gage. If the head pressure goes too 
high, the effects on the system are that less heat can be removed from 
the cold rooms and more power is required to operate, the compressor. 
The effect of various high head pressures on power requirements at 
various suction pressures may be seen in the accompanying chart, Figure 
2. For example, the chart shov^rs that operating at 25-pound suction 
pressure, if the head pressure is 120 pounds, about 1.0 hoi-sepower is 
required to remove 288,000 Btu per day (l ton of refrigeration) whereas, 
at a head pressure of 195 pounds, about 1.5 horsepower is required for 
removing heat at the same rate. That is, the pov;er cost is about 50 
percent higher at a 195-pound head pressure than at 120 pounds. At the 
same time, a high head pressure results in reducing the amount of heat 
that the system can handle. This is illustrated in Figure 3. 



14. 



200 

7- 




F GURE 2 


k- 




! / 

<v 






• 

■ 




o ^ •■ 

i. A •■ • 


#1 


/ 

/ 


/ 


I 

1 

- 40 


/ 

/ 

/ 

/ 

/ 

/ 

/ 

/ 


' " n 


r 

•.X- /•' 


/ 

/ 

f 
/ 
/ 


■ / 




.r-- 


1 ^./^^ 


/ 

/' 

/' 

/ 


^ 7^ 1 

/ 
/ 

/ 

/ 


/ 

/ 




O 
u 


/ 

/ 

/ 


/ 

/ 


/ 

A 




X 


' 


O 1 


S 2 


O 2 


s 3 


O 3 



SUCTiCN PlUSSURb -LBS. PER SQ.IN. 



EFFECT OrO^ERATiNG PRESSURiS UPON POWEK 
HEQJiREMENTS G)t A TOPICAL AMMONIA 
COMPKESSOR. 



FIGURE 3 



15. 



20Q 




O \b 20 2 5 • 30 

SUCTION PRESSURE - LBS' PER SQ 



J 



5 



N, 



EFFECT OF CONDENSING AND SUCTION 
PRESSURES UPON CAPACITY OF A TYPICAL 
AMMONIA COMPRESSOR. 



16. 

If the head pressure is too high v/hen the plant is running to ccipacity, 
it may be because of too small a condenser, not enough cooling v/ater, 
cooling water too v»rarm, presence of non-condonsible gases, or dirty 
condenser tubes. The water used in the condenser contains impurities 
which corrode the pipes and form deposits on them. This deposit in- 
terferes seriously with exchange of heat if it is allovred to accumulate 
over long periods, 

COt'IPRESSQR 

The compressor, by pumping ammonia from the evaporator to the condenser, 
takes the heat vj"hich has been absorbed in the coils and by raising the 
temperature, allows the heat to be carried av^ay by the condenser cool- 
ing v/ater. The rate of heat removal by a given ammonia compressor 
ninning at a given speed depends only upon the head pressure and the 
suction pressure at which it operates, the higher the suction pressure 
and the lower the head pressure, the more heat 'nvill be removed. If the 
speed is incruased, the rate of heat removal will increase proportion- 
ately, provided the pressures arc maintained the same. It is good 
practice therefore to operate a compressor at as high a speed as its 
design will permit during the season vj-hen v/arm fruit is being received. 
In fruit storage, the demand on the refrigerating equipment is at a 
maximum for only a short period in the fall. Lluch of the capacity of 
this equipment is idle during the rest of the year. In order to get 
the most out of it for this period vifhile keeping the investment in 
equipment to a minimum, it is sometimes economical to operate at higher 
speeds than vrould be advisable for year round operation. However, com- 
pressors should be speeded up only after consulting the manufacturer's 
representative regarding the particular machine. Greater capacity may 
be obtainable in some slov; speed compressors by changing the valves 
and lubrication systems to permit considerably higher speeds. 

It is a mistake to judge the capacity of a refrigerating system by the 
power of the motor installed to drive the compressor. For comparative 
purposes, capacity is sometimes expressed as standard tons, that is, 
the capacity of 155-pound head pressure and 20-pound suction pressure, 
for example; but the actual capacity will depend upon the whole system 
and not on the compressor or on the compressor and motor alone. 

EVAPQR/ITQR 

The evaporator, or cooling coils, absorbs "the heat from the room. The 
ammonia having had its load of heat removed in the condenser, is ex- 
panded to a vapor. This expansion, or evaporation, reduces the ammonia 
temperature to such a point that it is ready to pick up more heat from 
the cold room. This is done by direct expansion coils in the room or 
by air circulated from the room to o. bank of coils or finned surfaces. 
Here, as in the condenser, conditions should be such as to permit the 
heat to flow with as little temperature difference as possible between 
the ammonia and the air in the room. If there is not sufficient cool- 
ing surface or the surface is covered with frost or if other factors 
retard the heat flow, the aimnonia must be extremolj;" cold. This means 
a low suction pressure which reduces the capacity of the compressor. 
At low pressures the ammonia gas is less dense, and a smaller quantity 



17. 

of gas is drawn into the compressor at each stroke, resulting -in a 
lower refrigerating capacity. Figure 3 shov/s the, effect of various 
pressures upon the capacity of a typical compressor. It will be seen 
that the capacity is increased markedly as the suction pressure is 
raised. For example, at 140-pound head pressure the compressor illus- 
trated delivers 9 tons at a suction pressure of 24 pounds. An increase 
of 4 pounds in suction pressure changes the capacity, of the same machine 
to 10 tons. If by increased cooling surface or careful operation the 
pressure could be increased to 36 pounds, about 12 tons of refrigeration 
would be obtained, a gain of 25 percent. Similar changes in suction 
pressure in an ammonia machine of any size would result, in approximately 
the same percentage increase in capacity. 

Another .disadvantage of operating at low suction pressures is that the 
coils are extremely cold, and a large amount of moisture is condensed 
out of the air, resulting in lov/ storage humidity, Ample evaporator 
coil surface will pennit the cooling to be done without excessively 
cooling the air.. The result of cooling the air to lov/ temperatures is 
shown in the appendix, 

COLD STO.RZiGE ROOMS . . . •. • .. 

In direct t^xpansion rooms, that is, vrhere cold ammonia is circulated in 
exposed pipes v/ithin the rooms, the fruit is cooled by air v^hich is 
cooled by the pipe coils. The coils are in the upper part of :the room. 
Air in contact with the coils becomes coldj and cold air being denser 
than v/arm air, moves do-wnward. As it picks up heat from the fruit it 
v/arms up and again rises to the pipes to bu cooled. This, circulation 
caused by differences in air temperatures is called convection. Air 
velocities in convection currents are relatively lov/. If the pipes 
are v^fell distributed over the ceiling of a room and these low- velocity 
air movements are toJcing place in all parts of the room, fairly fast 
cooling can be obtained. On account of the problem of disposing of 
frost or water condensed on the pipes, they are usually put in groups 
or banks, and gutters for catching the drip are hung under them. In 
rooms where large areas of the ceiling are without coils, direct ex- 
pansion alone cannot cool the fruit very promptly, and there may be 
fairly large temperature differences betweezi various parts of the room, 
even after the fruit has cooled to its final temperature. In this case, 
either portable or permanent fans operating in the room stimulate air 
movement and tend to improve the temperature distribution. If fans, can '- 
be installed to give a positive air movement even better results may be 
obtained. Fans blowing directly over the cooling pipes may be effective 
in reducing condensation and limiting local freezing in the fruit. 

In the dry coil bunker system of cooling, the ammonia coils are put in 
a separate room or bunker and air from a large blower is passed over - 
the coils then distributed through ducts to the storage room. If large 
quantities of air are used, prompt' cooling and even temperatures may be 
obtained. The problem of accumulation of frost on the pipes remains, 
although disposal of the water and frost without damage to the fruit 
is simpler than vj-ith direct expansion. In some installations the pipes 
are defrosted periodically by spraying them with brine or warm unsalted 
water. The blower is stopped vfhile the defrosting is taking place. In 



18. 

other plants defrosting is done by pumping hot ammonia into the coils. 
Dry coil bunkers have largely given vm.y to brine spary systems in 
recent installations. 

In the brine spray system of cooling, air from a large blower is moved 
over banks of ammonia coils which are continually being sprayed with a 
solution of salt in water. The salt prevents accumulation of frost, 
and the fine spray, being in intimate contact vdth the air, cools it 
effectively. A far smaller bank of pipes can be used than in a dry 
bunker and cooling can be done with a higher ammonia temperature, Af- 
ter cooling, the air is distributed to the storage rooms. Vifhen a con- 
tinuous brine spray is used, it is necessary to use baffles or elimina- 
tors in the air stream to prevent particles of brine from being carried 
in the air to the storage rooms. It is also necessary to treat the 
brine with chemicals as recommended by equipment manufacturers to re- 
duce its tendency to become undulj'' corrosive. In spite of the necessity 
for eliminators which increase the resistance to air flow, and the 
tendency of the brine to cause corrosion, brine spray chambers are dis- 
placing both direct expansion and dry bunker systems in this area. 

A modification of the dry coil or brine spray bunker is the unit cooler. 
These coolers contain extended surface coils and blowers for moving the 
air through the coils and discharging it to the room. Some are defrost- 
ed by a continuous brine spray and in some the coils are washed periodi- 
cally with fresh v/ater to remove the frost. These units usually dis- 
charge air at the top, cither into ducts or through nozzles, and return 
it to the coils through openings near the floor. With the return air 
picked up in the lower part of the room, it is difficult to get the 
best distribution of temperatures. When defrosting is intermittent, it 
is important to make the cycle short enough to keep the coils fairly 
free from frost. A thin layer of frost interferes v/ith heat transfer 
just as with the other t],q)es of coils and on account of the close spac- 
ing of the cooling surface, frost also reduces the amount of air circu- 
lated. 

The humidity or moisture content of the air in a storage room depends 
"largely upon the temperature to which the air is cooled in contact 
with the pipes or the brine. 

If the doors are left open in warm weather, the v/arm air entering the 
storage may be a source of moisture, but the frost on the pipes or the 
overflow in the brine tank is largely from water evaporated from the 
fruit. It is desirable to keep this evaporation to a minimum by main- 
taining a relative humidity of approximately Sb%. This may be done by 
limiting the amount of water picked up on the coils or in the spray. 
A certain amount of water in the form of gas or vapor is contained with 
the air. The lower the temperature, the less the vapor that can be 
held. As the temperature of the air drops, a point is finally reached 
at which some of the water can no longer exist as vapor and it condenses 
to form water or frost. The greater the temperature drop, the greater 
the consequent condensation. It is therefore important to operate with- 
out reducing the air temperature lovfer than is necessary. In an air 
circulation system, this is done by using large quantities of air and 
plenty of cooling surface. If too little air is used, its temperature 
must be reduced greatly and excessive condensation will occur. In a 



19. 

direct expansion system if there is not enough coil surface, the pipes 
v/ill have to be extremely cold and the air coming in contact with them 
will lose a large part of its moisture. Contrary to common belief, a 
brine spray, when used for cooling, does not add humidity to the air. 
On the other hand it tends to pick up moisture from the air. That is 
why some of the brine must be drained off oocasionally and more salt 
added. If a brine spray system results in higher humidity than a direct 
expansion or dry bunker system, it is because it removes less moisture 
and not because it adds more. It removes less moisture because the 
surfaces with which the air comes in contact are not so cold. 

In all plants there is necessarily a variation of temperature in differ- 
ent parts of the room. This variation should be kept to a minimum. The 
equalization of temperature in all parts of the room depends almost en- 
tirely on circulation of air, either by convection or by forced draft. 
Convection cannot be depended upon for adequate circulation unless the 
whole ceiling area is flooded with cold air or provided with cooling 
coils. . _ _ 

As the air circulates in a storage room, it picks up heat, thereby 
raising its temperature. If it is not picking up heat, it is not doing 
any good. The air returning to the brine spray or dry bunker is there- 
fore warmer than that entering the rooni from the delivery ducts. The 
difference in temperature between the delivery and return is often 
referred to as the "split." The amount of the split is directly re- 
lated to the amount of air circulated and the amount of heat picked up 
in the room. If the split is too large, the only way to reduce it with- 
out cutting down the amount of heat picked up is to increase the volume 
of air circulated. It cannot be done by making adjustments of openings 
unless the adjustments result in greater volume of air. For each ton 
of refrigeration used, an air volume of 1,000 cubic feet per minute 
(CFM) results in a split of about 10°. (if water is being evaporated 
from the fruit and condensed by the coils, this relation is modified 
somewhat.) This relation applies to any combination of refrigeration 
being done, and volume of air, and resulting split. For example, if 
1,000 OFlIi of air is used in picking up the heat equivalent to 2 tons 
of refrigeration, the split will be about 20°, or if 2,000 CFlJi gives a 
split of 5°, about 1 ton of refrigeration is being supplied. It is 
customary to design air circulation systems so as to provide for about 
1,000 CFfil per ton of refrigeration capacity. For example, a 25-ton 
plant would circulate about 25,000 CM. This gives a split of about 
lO"-* when the machinery is working to full capacity. After the fruit 
has been cooled and some of the compressors are shut off or slowed doiivn, 
the same volume of air will result in a lower split. Vflien the refrigera- 
tion load is down to 5 tons and if 25,000 CFM is still used, a split of 
abgut 2° will result. In this case, a variation of at least 2° may be 
expected in the fruit temperatures in different parts of the room. ViTith 
less air volume the variation will be greater. 

If fruit were not living and generating a small amount of heat continu- 
ously, the problem of holding it at a uniform temperature would be much 
simpler. The heat generated must be given up to the air to prevent a 
rise in fnait temperature. In order to pick up this heat, the air must 
be slightly colder than the fruit and in picking up the heat the air 
temperature is raised slightly. For this reason it is not possible to 



■. • . 20. 

have the same air or fruit temperature in all parts of a storage room. 
In some rooms the variation may be kept dovm to a fraction of a de- 
gree while in others it may be difficult to avoid a variation of 
several degrees even aftei* the fruit has been cooled to its final 
temperature. 

On account of these variations in temperature, readings from a single 
thermometer in a room may be misleading. In order to operate a plant 
to best advantage it is desirable to know at least the highest and 
lowest temperature in each room. It is the core temperature of the 
fruit itself which deterraines hov/ well it will keep. It is sometimes 
difficult to take fruit temperatures in the parts of the room that 
are likely to be v;arm. Hov/ever, there are times during the season, as 
fruit is shifted or loaded out, when it is possible. . In many cases, . 
if temperature conditions are knorm, steps can be taken to improve the 
distribution. If actual fruit temperature readings arc not taken, there 
is a tendency to assume that the aisle thermometer shows a room- tempera- 
ture vfhich prevails at all points. This is not the case and large tem- 
perature variations may occur, especially for the first few weeks of 
storage. 

The storage season may be divided into ti^/o distinct periods — the first 
period is during the harvest v/hen v.^arm fruit is being put into the 
plant and the principal problem is cooling, the fruit or removing the 
field heat. The second is. the holding period when the main problem 
is maintaining low temperatures as unifgrmly as possible. The heat 
load during this. period is relatively low, consisting of the respi- 
ation heat generated by the fruit, the heat entering through the walls, 
and heat from incidental sources such as vrorkmen, power equipment, 
lights, and- entrance of --air from outside. 

.. . SOURCES OF liSAT 

A discussion of the various sources of heat to be removed by 8. refrigera- 
tion system is necessarily more or less techixical and includes terms 
which may not be fam.iliar. It is not difficult to follow, however, when 
it is kept in mind that heat is just as real as air or water. It can be 
moved from one place to another, but it cannot vanish completely. If 
heat is taken from one place, the same amount must shov/ up somevrfiere 
else. For this reason it is convenient to think of units of heat as 
quantities "vvhich have a definite meaning, just a.s -we think of gallons 
of water. A. convenient amount of heat is the Btu (British thermal unit). 
It is the amount necessary to rrise the temperature of 1 pound of water 
1° Fahrenheit. The important thing to keep in mind is that a Btu is a 
definite amount of heat that can be pushed around or divided up, but 
still exists somev^hore. 

A . refrigerating system is capable of taking a certain amount of heat 
from the evaporating coils and discharging it to the condenser cooling 
water. One-ton machines can take up 288,000 Btu every 24 hours by op- 
erating continuously, or a 10-ton rxachine can take ten times this amount. 
The capacity of the cooling system required for a given job depends upon 
how much heat must be removed each day. In apple storage this heat comes 
from several sources, each of which can be considered separately. The 
total load is the sum of the heat from all sources. 



21. 

-' X..j_iiJ ' U_|J 1 

Fruit, ■./""hen placed in stora.x, is ordim.rlly a te'aperature hi;hGr than 
that desired in storage. The hce.t to be re loved in rcducin;; the frait 
tenp era tare is called field heat. It takes about ,9 13tu to chanj^-'e the 
tetiperature oT 1 pound of a^.., Ics b./ 1°« If the tenpcrature inaust be 
reduced from G5"^ to 32°, for example, the chanr;e is 33° and for every 
pound of a^-'ples 29.7 (.9 x 33) Btu aust be reuovsd. On the assumption 
tb.ut a box of apples wcij^hs bO ^jOunCr.:, evciy box cooltd from 65° to 32 
requires the reaoval of 1,^35 (29.7 x 50) Btu. If 1,000 bo es arc put 
into storai;;e, under these conditions, 1,485,000 3tu of field heat are 
introduced into the storage rooa. If the fruit is cooler or waraer, 
the heat load v;ill be correspondin.^ly less or f.reater. 

}IE/.T O:^ ;J'=5.cI.i:iTI0i: '■ ' ' ..:•■•.-..- 



Fruit continues to live as Ion-; as it is fit for food and is therefore 
continually ;;eneratin[^ heat by breaking do vn some of its constituent 
materials. I'he rate at 'vhich this hoat is fjenerated depends upon the 
fruit tCu\;eraLure» At 62° a box of Delicious apples ^-^ives off about 
20 Btu each day. At 60° the fi^;ui'e is seven or ei^ht tiaes as reat. 
i-roiap coolin;.^, therefore, reduces the tot'il aiaount of heat to be re- 
moved from a storape rooa. It is estiiriated that if fruit is cooled 
froa G5° to 35° in a week, the heat of res_^'iration froui a packed box 
of apples d.urin(;, this period will aaount to about 500 Btu, or for 1,000 
boxes the hea': load would be 500,000 Btu, or about a third as ^'auch as 
the field heat load. If coolm,_ is so slow that it takes t.vO '.veeks to 
reach 35 deprees, another oO'0,000 Lltu will have been j^cnerated. '-ven 
a^ter the apples are cooled to oS'^, th^' continue to pive off heat, 
iach 1,000 boxes generates about iiO,000 75tu per day at tliis temperature. 
Thus, 1 ton of refrit^eration (renoval of 2^^3,000 .Jtu per day) v:ill take 
care of the heat frori about 1^-,000 or 15,000 boxes after i hey arc cooled 
dovm. 

IirciJiLUTAL IILiU' SOU.jCEG ■-•v;. •••. , ' 



In addition to the fr-iit itseli", other sources i_,eneratin£ iieat are any 
men, raotors, and liputs. It laipht be assu/acd that each \/ork-'ian ,-,ives 
off 1,000 iitu per houi". The heat froa notors can be estimated at 2,500 
Btu per hour for each horsepO'..'er. If a /notor is act-ually delivering; 
its rated horsepo'.ver, the total heat given ofi v/ill be soiae.hat „;i-cater. 
Each 100 watt lijj;ht burning adds about. 350 Jtu per hojr. 

Alii Ii:7iLT':.^M0N 

There are always tines v/hen it is necessary to leave outside doors or 
conveyor plups open, and in soiie roo.ns doors- are open almost continu- 
ously during the harvest season. Outside air entering; the cold room 
may carry in lar^^e amounts of heat. It is impossible to estimate very 
accurately the heal load added by infiltration of air under ordixiary 
conditions. If vje assume that a draft of 200 feet per minute is leav- 
ing a cold I'oom at 35 thron, h the lower half of a door 4 feet ■..■ide and 
7 feet hi;;h, and an equal current of Cry ">."ara air at 65^ is enterin^'; 
the upper half, an estimate of the entcrinj^ heat can be inade; 200 feet 



22. 

per minute is about 2-^ miles per hour and is not a very noticeable 
velocity. However, under these conditions, 100,000 Btu per hour 
would enter through the open door. If the air were not very dry the 
amount would be even more. It would keep an 8-ton machine busy just 
to remove this heat. Actually it is next to impossible to keep the 
room temperatures down with the door open continually; the air leav- 
ing the room is considerably warmer than 35°, and the loss of refrig-. 
eration may not be as large as this estimate. At best, open doors 
cause a large entrance of heat or loss of refrigeration and prevent 
holding low temperatures in the room. For this reason it is desirable 
to use small openings covered with canvas flaps for loading cold stor- 
age rooms. YPaen it is necessary to use hand trucks and keep full-size 
doors open, light swinging doors which close after each truck has passed 
will reduce the loss of refrigeration. 

HEAT PASSING THROUGH INSULATION 

Even when there is no infiltration of air through doors, window, or . 
cracks, there is an unavoidable entrance of heat through the walls, 
floor, and roof when the outside of these surfaces are v/armer than 
the inside. The amount of heat entering through the walls may.be re- 
duced by insulation which slows the passage of heat by resisting its 
flovj-. The amount of resistance depends upon the character of the in- 
sulating material and its thickness. Perhpas the most convenient com- 
parison of the effectiveness of various insulating materials can be 
made by showing thicknesses which' will pass equal amounts of heat un- 
der similar conditions. In many cold storages, 12 inches of shavings 
are used for insulating the walls. Table III shows the thickness of 
various materials required to equal the resistance of 12 inches of 
shavings. The thicknesses shown are based, on the conductivities pub- . 
lished in the American Society of Refrigeration Engineers, Refrigera- 
tion Data Book. 

Table III 

RELATIVE HK^T RESISTAI-ICE OF VARIOUS MATERIALS 



Material 



Thickness Equivalent to 
12 Inches of Mill Shavings 



Planer shavings 

Corkboard 

Redvraod bark fibre 

Celotex 

Pumice gravel 

(Grains 1/33 in. to 3/IS in. diam. ) 18.8 lb. 

Fir, across grain 

Concrete 

Cinder concrete 



8.74 


lb. 


per 


cu. 


ft. -12 
ft.- It 


inches 

inches 


5.04 


lb. 


per 


cu. 


inches 










9i 


inches 


18.8 


lb. 


per 


cu. 


ft. -19 

-29 

156 

72 


inches 
inches 
inches 
inches 



The amount of heat passing through a v^rall with 12 inches of dry shav- - 
ings depends upon the temperature difference between the two sides. 
When it is 65° F. outside and 32° inside, eachlOO square foot of such 
a wall may be expected to permit passage of about 2,600 Btu per day. 
That is, 11,000 square feet of such a wall will permit the loss of 



23. 

about 1 ton of refrigeration. Approximately the same amount would be 
passed by equal areas of the various materials shown in the table if 
they were of the thickness shown. For walls twice as thick, the heat 
flow would be only half as great; or for a wall only one-third the 
thickness sho-wn, three times as much heat would pass through. 

It should be pointed out tliat for fill insulation, such as shavings, 
sawdust, and redwood bark fiber, the resistance is influenced by the 
density of packing. In vertical walls, especially, such materials 
need to be packed in tightly enough so that settling does hot occur 
and leave unfilled spaces s.fter the wall is closed up. In the above 
comparisons of various materials it is assumed that they are dry. 
Moisture in all these materials reduces their effectiveness and v.''ill 
cause some of them to rot. They should all be installed so that they 
will not accumulate moisture. There is a tend.6ncy for moisture to con- 
dense on surfaces cooler than the air but not on those warmer than the 
air. The insulation material in a wall or roof is usually colder than 
the outside air. It is therefore important for the insulation to be 
protected against the outside air by a barrier against water vapor, 
such as coatings of asphalt or vapor-proof paper. A barrier is usually 
not necessary on the inside of the wall since there is seldom s. tendency 
for a wall to pick up moisture from the inner or cold side. In fact any 
moisture that m.ay be present in the wall will tend to evaporate from the 
vra.ll and condense on the cooling coils in the room. For this reason, a 
vapor barrier on the inside or cold -side of an insulated wall may do 
more harm than good. 

■ ■' PSECOOLIrIG "'"■'■'■ /■"■,.-•' 

Precooling is usually spoken of as a special process for the rapid re- 
moval of heat from a coraraodity before transportation. The term is also 
used in the Pacific Northwest to denote heat removal preliminary to 
stacking In storage. In precooling winter pears before stacking in 
storage, usually the fruit is packed, but with apples it is more often 
done while the fruit is loose in field boxes. For hard varieties, such 
as Winesaps, such special stacking for precooling is not often used. 
For softer varieties, especially Delicious, the importance of prompt • 
cooling is being recognized more and more; and arrangements for pre- 
cooling are being installed in an increasing niam.ber of plants as fast 
as economic and war conditions permit, . . 

Probably the most effective present method of precooling pears and 
apples is to stack the fruit in relatively small rooms and circulate 
a large volume of cold air. The advantage of a small room is that 
after cooling has been started, it is not necessary to bring warm fruit 
into the same room. Yfiiere a number of small rooms are used,' each can 
be filled in turn rnd cooled while others are being filled. This ar- - 
rangement, however, cannot be installed mthout additional expense, and 
the cost of handling the fruif is apt to be high. For this reason cool- 
ing is usually done in larger rooms in which warm fruit is being received 
more or less continuously during the cooling period. 

The value of any special arrangement or process for precooling is 
measured only by the completeness and promptness with which the fruit 



24. - 

is cooled. Any arrangement whereby fruit is put into a cooled room 
prior to final stacking in storage is loosely referred to as "pre- 
cooling."" It is obvious that if it does not result in quicker and 
more thorough cooling, it cannot be of much benefit. If such an 
arrangement provides only for distributing an inadequate cooling 
capacity over a large number of boxes during the receiving period, 
there is very little, if any, net gain to compensate for the extra 
handling. Little is gained by rushing fruit into cold storage rooms 
if the cooling it receives is at the expense of the fruit already 
there. If apples are received in a storage or precooling plant at 
such a rate that the compressors are required to operate continuously, 
further increases in receipts of v;arm fruit will result in partial 
cooling of a larger amount of fruit but less effective cooling in each 
box. 

In many storage plants there is little danger of freezing fruit during 
the period of heavy receipts because of insufficient refrigeration. 
In certain plants, however, the full refrigerating capacity cannot be 
used for rapid cooling on account of the danger of freezing fruit at 
points near the air delivery. This freezing can be avoided and a more 
uniform temperature can be obtained throughout the room if there is 
provision for reversing the direction of air movement periodically. 
That is, every fexi hours, or as often as is necessary, the circulation 
will be adjusted so that air is delivered from the return ports and 
taken off in the delivery ports. This arrangement will provide for 
rapid cooling of all the fruit without danger from freezing. If such 
an arrangement is used, its full advantage will be obtained only if 
adequate refrigeration is available and sufficient volume of air is 
circulated. 

STOR/iGE PERIOD 

After the fruit is cooled and no more warm fruit is being received, the 
amount of refrigeration required is far less than during the cooling 
period. There are very few plants lacking in refrigerating capacity 
during the storage period. The problem is to maintain proper fruit 
temperatures in all parts of the room without danger of freezing in 
boxes near the air delivery or cooling coils. This uniformity of 
temperature depends almost entirely upon air circulation. Some heat 
usually enters through the walls and the fruit generates some. This 
must be picked up by the air and carried to the cooling coils. If 
insufficient air is circulating, the rise in air temperature before 
returning to the coils will be excessive, and some of the fruit will 
be exposed to the warmer air. It is usually not advisable to reduce 
the air circulation after the cooling 'period is over even though far 
less refrigeration is required. However, there are some plants in which 
the air volume is so great that little is lost by reducing it, A good 
way to judge vrhether the volume might be reduced is to check the tempera- 
ture of the air entering and leaving the room. If the difference between 
these is less than l^'-', some reduction in air volume might be justified. 
It is more economical to do this by reducing the fan speed than by re- 
stricting duct openings. 



25, 
STORAGE DESIGN 

The first requirement for a satisfactory cold storage plant is that 
sufficient refrigeration is available to cool the fruit as fast as it 
comes in . It is estimated that for each 1,000 packed boxes received 
into storage daily, 8 tons of refrigeration is required. 

The next requirement is that there be sufficient air movement to dis- 
tribute the available refrigeration . In blower circulating systems 
there should be at least 1,000 cubic feet of air per minute for each 
ton of refrigeration. In direct-expansion systems the air movement is 
most satisfactory if the cooling pipes are well distributed over the 
ceiling -area. 

It is important that the return air be taken from the room at the points 
of highest air temperatures . In general, these are in the upper parts 
of the room. 

If the above conditions are satisfied, it should not be difficult to 
obtain good cooling. 

In some plants it is difficult to got the warmest air to the return 
ducts. This is most easily accomplished if the returns are near the 
ceiling, if there is ample space between the top boxes and the ceil- 
ing, and if there are no obstructions to air movement along the ceil- 
ing. Structural members, such as girders and joists, may impede the 
air movement. Vlhere the joists are ceiled and the girders are under 
the ceiling, the direction of air movement should if possible bo parallel 
to the girders. On the other hand, if the joists are set on top of the 
girders and the joist space can be left unceiled, the direction of air 
movement should be parallel to the joists. 

In laying out a building to be used for cold storage, the best results 
will be obtained if the details of the refrigerating system and those of 
the conveyors and other fruit-handling equipment are considered in the 
plans. The location of structural members, doors, and openings can then 
be worked out for most advantageous fruit handling and cooling. Loca- 
tion of girders so that they interfere with air movement can be avoided, 
and fruit handling processes can be fitted in with distribution of re- 
frigeration to best advantage. 

Shavings insulation is well suited to the Pacific Northwest on account 
of its low cost and the relatively dry climate which lessens the problem 
of protecting it against moisture. For use on the ground floor, pumice, 
of which natural deposits are found in this area, is a good insulator 
that is not damaged by wetting. 

Y/hether or not to insulate partitions and interior floors depends upon 
the use to be made of the rooms. In most plants all the rooms are usu- 
ally refrigerated at the same time. Unless there are times when rooms 
will be cooled individually, special provision for insulation between 
rooms and between floors is not necessary. Sometimes insulation used 
in the joist space of a ceiling is a disadvantage. If the joists run in 
the direction of the air movement and are set on top of the girders, the 



26. 

joist spaces provide air channels over the boxes v/hich are lest if the 
room is ceiled and insulated. 

The design of air ducts has an important bearing on the amount of air 
that can be circulated by a blower. The resistance to air flow is 
greatest in- the- sections where the velocity is high and at points where 
the air changes velocity or changes direction. Abrupt changes in area 
of ducts or unrounded turns should be avoided. The inside of ducts 
should be free of obstructions and as smooth. as possible. Vfhere ob- 
structions -such as posts or girders cannot be avoided, it is worth 
while to ease the flow of air around them by installing baffles to give 
a streamline effect. This is particularly true at points vfhere the air 
velocity is high. Large ducts are preferable because they permit de- 
livery of the required volume of air with,out excessive velocities. 

YTnen a new plant is to be installed or additional equipment is being 
considered, it is always important to avoid excessive costs. At such 
times the first cost is frequently a chief consideration in deciding 
what equipment to purchase. Usually when the cost of a proposed job is 
learned, it seems excessive, and there is a tendency to look for items 
which may be eliminated or reduced. It is poor economy to cut dovm 
first cost by unduly limiting the cooling surface, the condenser capa- 
city, or the size of fans and ducts. Many plants are handicapped by 
having too small a fan, or ducts Vvrith too much air resistance. In- 
creasing the speed of a fan to get more air circulation does so at a 
cost of more power for each cubic foot circulated. For this reason it 
pays to install a fan having the required capacity at moderate speed. 
Ducts too small in cross-section or causing unnecessary turns in the 
air streams, build up resistances which result in high power consumption 
or insufficient air circulation. There are two reasons for keeping the 
power requirement to a minimum. First, the fan operates over a long 
period in the year, and the cost of povrer to drive the fan itself may 
be a large item. Second, the povrer used on the fan adds heat to the 
circulated air. This heat adds to the refrigerating load, and thus 
reduces the useful capacity of the refrigerating machinery. Each 
horsepower used on the fan puts a load of .2 to ,3 h.p. on the com- 
pressor motor. 

MAMAGEIJEKT 

During the cooling period many plants take in fruit faster than their 
equipment can cool it. As a result the fruit is not cooled to the hold- 
ing temperatures until late in the fall. Y»hen this is the case, every 
effort should be. made to use the available refrigerating equipment to 
the best advantage. Compressors and auxilliary apparatus need to be in 
good shape. Condensers should be clean and all available condenser 
surface used. Evaporating coils should be kept as free as possible from 
frost and blowers used to circulate the maximum amount of air. If, dur- 
ing this period, it is necessary "to shut off some of the compressors to 
avoid local freezing while fruit temperatures are too high at some points, 
the capacity of the equipment is not being used to fiall advantage, and 
some means for better distribution of the refrigeration should be found. 
This usually may be done by improving the air circulatioia or inesreasing 
its volume. IfVhile ample air circulation cannot compensate for inadequate 



27. 

refrigeration, it does permit maximum use of the refrigeration avail- 
able. 

REDUCING INITIAL FRUIT TEIiIPERATURE 

The amount of heat that must be removed from a box of apples depends 
largely on how hot it is when put into storage. If the average tempera- 
ture of the fruit can be reduced before storing, the load imposed on the 
plant by each box is lessened. Apples or pears picked in the afternoon 
are ordinarily hotter than those picked in the morning. Picked fruit 
in boxes left under the tree is considerably cooler in the morning than 
at evening. For these reasons, there are a number of advantages in 
bringing fruit to cold storage in the morning hours only. Hot fruit 
left loosely stacked under the trees over night may be cooler by morn- 
ing than if placed in a crowded storage room. By leaving it out to 
cool over night, the fruit already in storage has a chance to cool 
faster. In short, the condition of the fruit can be improved and the 
number of boxes the plant can handle satisfactorily can be increased. 
The advantages to be gained by eliminating afternoon receipts, especially 
in plants of limited cooling capacity, warrants the adoption of this 
practice even at the expense of some difficulty in handling and hauling. 

SEGREGATION OF LONG STORAGE APPLES v "' . '' 

The Delicious variety causes the most serious problem in the Wenatchee- 
Okanogan area, because of its storage temperature requirements, the large 
tonnage of the variety, and its relatively short harvest period. If 
there were enough cooling capacity to cool all the Delicious apples as 
fast as they are harvested, it would be desirable to cool. them all as 
quickly as possible. Since this is not the case, an attempt to cool all 
of this variety with equal promptness means that none of it is cooled 
quickly. In general, the longer a box of Delicious is to be held, the 
more important it is to cool it quickly. This suggests that long-storage 
lots of fruit should get more than an equal share of refrigeration at 
harvest time, and short-storage lots, less. Perhaps this can only be 
done by determining before harvest which lots are to be held for long 
storage and which are to be moved early. The fruit would then be 
treated accordingly. Those for long storage would be put in rooms in 
which the receipts would be limited to an amount that would permit fast 
cooling. Fruit for shipment during the harvest season or ivithin a few 
days of picking would be deliberately virithheld from any precooling in 
order to save the refrigeration for long-storage lots. Apples for in- 
termediate shipment would be cooled as quickly as possible without 
ponalizing the long-storage lots. This, of course, involves more plan« 
ning before harvest than does a procedure whereby all Delicious in stor- 
age, but such planning would be justified by the improved condition of 
late shipments. It should be emphasized that such sacrifice in cooling 
early shipments is desirable only when limited capacity prevents prompt 
cooling of the entire Delicious crop. 

SEGREGATING TO AVOID SOFT SCALD 

Development of soft scald in Jonathans and other varieties, including 
Winesaps, is sometimes induced by a quick reduction in fruit tempera- 



28. 

ture to 32° after the fruit is somewhat advanced in maturity or is 
delayed after picking before going into storage, "vinien such delays 
are unavoidable, the disorder may be avoided by holding at 36 or 
above for the first few weeks of storage. Considerable soft scald 
appeared in Winesaps for the 1941 crop, and it was probably largely 
due to a low storage temperature after the fruit had been held in. the 
orchard or in cominon storage. Y^en it is impossible to get these 
varieties into cold storage promptly, they should be cooled only to a 
moderate temperature and segregated for early disposal. It is there- 
fore highly desirable to avoid putting them in the same room v/ith De- 
licious which should be held at 30° to 32°. Storage in separate rooms 
in which the temperature can be controlled independently is desirable. 
The fruit will not keep so long at this higher temperature, but the 
risk from soft scald will be avoided. 

PLANT OPERATION 

A cold-storage plant represents a relatively large investment in 
machinery and construction. Such investment can be justified only if 
it increases the value of the fruit stored. The value of a plant in 
maintaining fruit condition is largely determined by the way it is 
operated. Even the best designed plant with automatic equipment needs 
more or less continuous attention to insure the best results. 

CORE TEI^ERATUHE 

In order to make the best use of a plant, it is important to know what 
temperatures are being maintained. One or tvro thermometers for show- 
ing aisle air temperatures do not indicate the performance of a plant. 
An operator needs to know core temperatures of the fruit, especially 
in parts of the room where cooling is difficult. Periodic observations 
of fruit temperatures will indicate to an operator what methods of 
stacking and air distribution give best results and will show what parts 
of the room need special attention. Reliable thermometers are necessary 
for this purpose, and an investment in equipment for securing accurate 
records of temperature in all parts of a storage is very worthwhile. 

Frequently v;-hen actual fruit temperatures are measured, the results are 
disappointing. If they are, it is sometimes possible to improve con- 
ditions markedly with little cost or inconvenience. In any case, it is 
to an operator's advantage to know just how quickly he can cool a load 
of apples and how uniform he can hold the temperatures after they are 
cool. 

AIMONIA PJRESSUHES 

Routine observation of the gage pressures on the refrigeration equipment 
should be made. If the suction pressure goes too low or the head 
pressure too high, these are signs that the system needs attention. 
Ordinarily suction pressures below 20 to 25 pounds indicate that the 
cooling coils are not picking up heat as readily as they ought to. Head 
pressures over 160 to 170 pounds indicate lack of sufficient cooling in 
the condenser. These limits depend upon the kind of system used, but 
the cause of any unexpected changes in pressure should be found and 
corrected. If the pressures are normally outside the above limits, the 



29. 

possibility of making adjustments or changes in the inst?.llation should 
be investigated in order to reduce power consumption and get more re- 
frigeration. Suction pressures as high as 35 to 40 pounds and head 
pressures as low as 100 to 120 pounds can be obtained under favorable 
conditions. Pressure gages should be checked for accuracy occasionally 
since thoy may go out of adjustment after long use, •. 

STACKING BOXES 

It is customary to paint lines on the floor of storage rooms to indicate 
the placing of rows of boxes. Such lines facilitate even stacking. It 
is important to maintain the space bertween rows at all points. A uni- 
form spacing of 2 inches between roTfs has been found in tests to be 
practically as effective in permitting cooling as spacing up to 5 or 6 
inclieSj if there is sufficient head room between the boxes and the ceil- 
ing. Careless stacking, however, in which some boxes in one row touch 
or approach those in another row, restricts air movement and retards 
cooling. It has been found that a spacing of about 3 inches is needed 
in order to release box trucks when trucking fruit into rov/s, and con- 
venience in trucking has regulated spacing in most storage houses. To 
overcome slight irregulai-ities in stacking, 3 inches may be considered 
a satisfactory spacing for the bottom boxes. The rows should be laid 
out so that the general direction of air movement is along the -rovj's of 
boxes instead of across them., •• . ■ ^ '■ . ■. 

TiThen fruit is stacked too close to the ceiling, air movement is re- 
stricted and cooling cannot be. evenly distributed. No rule has been 
established on the minimum space required over the boxes to permit good 
circulation, but it is good practice to leave a space of several inches 
even if the ceiling is free from girders or other obstructions. 

In large rooms warm apples may be brought in over a long period. This 
means that fruit vdiich has been in the room for some time and should be 
cold is sometimes Vv-'armod up by incoming fruit. This effect is unavoid- 
able in some rooms but by judicious stacking, it can be kept to a mini- 
mum. In some cases it is possible to stack the first finiit brought in 
nearest to the air discharge ports so that after it is cooled it is 
not exposed to air coming off of v/arm fruit brought in later. In plants 
that have two levels with a slotted floor between, it is good practice 
to load the lov/er floor first so that fruit already cooled is not sub- 
jected to warm air rising from v/armer fruit below. 

AIR CIBCULilTION ■ ' . . " 



In most storage rooms the air circulation is planned so that the primary 
air movement is over the tops of the boxes and through aisle spaces. 
The cooling in the interior of the sto.cks is accomplished partly by 
secondary or convection currents up and do\\m. the spaces bet^^j'een boxes. 
This cooling is effective only insofar as the warm air Y\rhich rises to 
the ceiling is moved avray and replaced by colder air. The reason for 
leaving a reasonable amount of sapce overhead is to permit sufficient 
circulation for carrying off the heated air. If the space is limited, 
there is a tendency for the air to move along aisles or unfilled chan- 
nels in preference to the ceiling space. 



30. 

If the primary air circulation can be fo.rced to move through th"e spaces 
between stacks, more rapid cooling can be accomplished. Reducing the 
space over the boxes v/ill tend to move more of the primary circulation 
through the spaces, but it will also divert more of it through aisles 
or other open channels] and unless such channels are avoided, loading 
close to the ceiling or putting baffles across the ceiling to force 
more air into the box" spaces may result in moving most of the air through 
the aisles where it is least effective for cooling. 

For storage rooms in which relatively slow cooling will be tolerated, 
the type of circulation which provides for flooding the ceiling space 
with moving air and depends upon convection to cool the interior of the 
stacks will provide fairly uniform temperatures throughout the room with 
a minimum of care in laying out the loading arrangement. If-, in order 
to hasten cooling, the primary air is forced through the space between 
boxes, the ceiling space is sacrifiopd, and the natural convection 
from the ceiling space down into the stacks is greatly reduced, but the 
forced circulation among the boxes gives better cooling on account of 
the higher air velocity. It will be seen that if the convection cooling 
is sacrificed by reducing the ceiling space, it is important that forced 
circulation take its place. Otherwise the effectiveness of cooling will 
be reduced instead of inereased. For this reason, if an attempt is made 
to force air through the box spaces by cutting dovm circulation over 
the load, great care must be exercised in arranging the boxes. Uniform 
spacing becomes even more important and air channels which v/ill permit 
diversion of air around the stacks of boxes must be avoided, Precooling 
rooms in which these conditions are met provide much faster cooling than 
rooms in v/hich convection is depended upon for cooling the interior of 
the stacks . 

FROSTED COILS 

Accumulation of heavy layers of frost on cooling coils should be avoided. 
Pipes or finned coils need to be defrosted frequently to get the most 
from a cooling system. Disposal of the ice and water from defrosting 
may be a problem in direct expansion plants but removal of the frost is 
important especially during the cooling period, 

BRIIIE TREATLIEIJT 

In brine-spray plants the frost is washed off with brine. The water 
which would other.vise be on the coils is continually diluting the brine 
making it necessary to drain off some brine at intervals and add more 
salt. The brine should not be any stronger than is necessary to prevent 
accumulation of ice. One objection to brine spray systems is that upon 
exposure to air, the brine tends to become acid. Unless this tendency 
is checked, the particles of brine carried by the air are very corrosive 
and may damage any metal v;ith which they come in contact. The brine may 
be treated \vith a chemical to retard this corrosive effect. The instruc- 
tions regarding such treatment, which are furnished by the ice machine 
company installing the equipment, should be followed carefully. Such 
instructions should be .requested if they have been lost or forgotten. 



31. 

COITDENSER CARE 

The water used in condensers leaves a deposit on the pipes which inter- 
feres with heat transfer if allowed to accumulate. The water tubes of 
a condenser should be examined at least once each year preferably prior 
to the harvest season, to make sure they are in good condition, and if 
necessary given a good cleaning. 

CAHE OF COIgRESSOR 

The compressor and other machines, including motors and pumps, need care- 
ful attention. Instructions furnished by the ice, machinery companies 
should be kept in the engine room and referred to frequently. These 
instructions should cover operation of the particular machines in the 
plant. Carelessness in operation or failure to observe the recommended 
routine may prove expensive in repair or replacements. 

CONTROLS :. , ■ . ■ ■'- . -■ 



There are numerous types of controls used in various plants. The auto- 
matic pa2'ts of the equipment usually depend upon changes in temperature 
or pressure, or are controlled by clocks. It will pay to become familiar 
v/ith the principle of operation of each item involved in automatic con- 
trol. . . . ■ , ■ . 

FANS AND DUCTS .'-'., -"■',-'. '-' . .- ■ ' ■ . " '..■'''■■ 

In air circulation systems, the fan size and speed are usually selected 
to deliver a certain volume of air against an estimated resistance in 
the system. By keeping the resistance as low as possible, a maximum 
volume of air will be circulated. Frequently a fan will be found to 
have a film of dirt and grease accumulated on the blades and interior. 
This interferes with the air flow and should be cleaned off occasionally. 
In operating the dampers and openings in ducts, they should be as wide 
open as v/ill permit the desired air distribution. In making adjustments 
the ports requiring more air should be opened to full capacity in prefer- 
ence to closing dovm dampers or openings at other points. "liVhen the de- 
livery temperature of the air is too lov;/-, ports should not be closed 
doivn to prevent freezing. The temperature of the air should be raised 
instead, and as much volume as possible permitted to circulate through 
the room. In many plants there is too little air circulation. This 
results in high temperatures in parts of the room and sometimes an 
attempt is made to correct this by lov/ering the delivery air tempera- 
ture. If this becomes too low for safety, closing down the openings 
to prevent freezing aggravates the condition instead of improving it. 

FREEZING NEAR COILS 

In direct expansion rooms, the boxes nearest the coils sometimes become 
too cold even though other fruit in the room may be too warm. Frequently 
this happens because the boxes themselves are radiating heat directly to 
the coils, even though the air next to them may be above the freezing 
point. In this case, increased air circulation may keep the boxes from 
getting too cold or it may be necessary to put a shield between the boxes 



32. 

and the pipes. This shield is not for deflecting the air but is to 
prevent direct radiation, that is, to stop the "shining" of heat from 
the box to the cold surface of- the pipes. This "shining" or radiation, 
takes place regardless of the temperature of the air between the box 
and the pipes. 

KEEPING EQUIFMEOTT BALANCED 

To get the best results from a plant, the various steps in mechanical '.:." 
removal of heat need to be balanced. That is, the heat picked up in 
the room must be transferred from the fruit to the air, from the air 
to the cooling coils, from the coils to the compressor, and from the 
compressor to the condenser, where it is discharged to the cooling 
water. If in one or more of these steps the quantity of heat that can 
be transferred is unduly restricted, the equipment performing the other 
stops cannot be worked to its greatest capacity. The condenser is doing 
its part if the head pressure is not excessive, and the cooling coils 
are not unduly limiting the capacity of the plant if the suction pressure 
is well up. It is less simple to know if the air circulation system is 
in balance v;-ith the rest of the equipment. During the cooling period 
when the refrigerating equipment is operating to full capacity, the 
volume of air circulation may be considered in balance if the tempera- 
ture difference betvreen delivery and return air does not exceed 10°. 
A lower split is desirable but if it is greater than 10° an increased 
volume of air circulation will be found beneficial. As the load is 
cooled dovm and as less v/arm fruit is brought in, the split will decrease 
and should reach 1° to 2°. If, after the fruit temperatures become about 
stationary, the split exceeds l-|-° this is an indication of insufficient 
air volume. During this later period further cooling is not required, 
but it is necessary to maintain uniform temperatures throughout the 
room. Uniformity of temperatures depends first on an adequate volume of 
air. If the volume is sufficient, as indicated by the split between 
delivery and return, and temperatures in some parts of the room are still 
too high, the air is not being distributed to best advantage. This may 
sometimes be corrected by readjusting the delivery or return openings, 
giving special attention to increasing the volume of air entering the 
return ducts near the points of highest temperature. 





Average Freezing Temperat 


ures 




of Various Fruits 


• 




Commodity , :-. _. .-._...:-' Degrees Fahr. 




Apples 






Delicious - , .-■ ' - ■' ' 


28,36 : 




Jonathan "" ' 


28.35 : 




Winesap 


28.24 




Pears , . ■ 


1 




Bartlett hard ripe 


28,5 




Soft ripe ;... r/ ' ' •'' ■ ■ 


27.8 - ' --' • ':■''" 




Anjou hard ripe 


26.9 - ; 




Soft ripe 


27.2 




Cherries 






Bing - mature (black) 


24.1 i 




Bing - immature (bright red) 


I 

25.3 




Sour 


28.0 




Peaches 






Elberta 


29.7 




J. H. Hale 


29,6 ■ 1 




Appendix No. 1 









Approximate Refrigeration 


Re 


quired 












for 
















Delicious Apples 










For 


receiving 


1000 


boxes daily and cooling f 


ruit to 


32° F. 




in 


seven days 


. (Al 


.lovTance for open doors. 


, workmen. 


motors. 




etc 


. , may increase 


this requirement by 15 


or 


20^.) 






Initial Fruit 


Temporaturo Tons of Refrigc 


ration 








55 




4.9 










65 




6. 


,9 










75 




8, 


8 










85 




10. 


8 








For 


holding, s 


Lftor 


reaching 32° each 1000 


boxes requires about 


.07 


T. 1 ton 


of refrigeration vdll care for 


about 


15,000 boxes. 


- 






Appendix No. 2 











Space Required by Standard Boxed Apples 



-■ ' ■ , ■ Packed Loose 

^^^ight . . ,. . 1,0 Feet .91 Feet 

"i^idth ,1.13 ■" ' , 1.03 

Length ■ 1.63 ' . .. 1.63 

Length required for 3" spacing 1.88 . 1.38 

Net Cubic Feet per bo:c, 3" spacing 2.12 Cu. Ft. 1.93 

In estimating gross space required in a storage room, 
allov»rance must be made for aisle space, conveyors, v^all 
ceiling clearance, duct or piping space, and other space 
not actually usable for boxes. I.iaking these allovv^ances, 
a gross space of 2.5 to 2.7 cubic feet per box is some- 
times used. 

Appendix No. 3 " • 









ilaxinun Relative Humidity oi 


' ^ir 






i 

i 


[f 


air is chilled to: 


1 
and its temperature then raised to: 






24° 26° 

• 1 


28° 1 30° i 32° 

1 i 


34°j 36°- 


38° 


40° 




16° 


68 62 


57 52 


47 


43 


i 40 


37 


33 




18° 


75 


68 


62 57 


52 


48 


j 44 


41 


36 




20° 


83 


76 


69 63 
1 


57 


53 


49 


45 


39 




22° 


91 


83 75^ 1 69 I 63 

i 


58 


1 

i 54 


49 


44 




24° 


100 


1 
91 83 ' 76 69 

1 i 


64 


1 

59 


54 


48 




26° 




100 


91 83 76 

1 


70 


64 


59 


53 




28° 






100 91 I 83 

■ i 1 


77 


71 


66 


58 




30° 








100 


91 


84 


73 


72 


64 




32° 


■ 








100 


92 


85 


79 


70 











Appendix iJo. 4 




1 









sodiuli chloride brine 


Specific 
Gravity 


Pounds salt 
in lOO^f: of 
Brine 


Freezing 
Point 


1 

Density 
Pounds per 
Gallon 


1.00 





32.0 


8.33 


1.02 


2.8 


. 29.1 


8.50 


1.04 


5.5 


26.0 


8.67 


1.06 


8.2 


22.7 


8.84 


1.08 ■ '■^■ 


10.9 ■■ 


19,0 


9.00 


1.10 


13.5 


14.9 


9.17 


1.12 


16.1 


10.4 


9.34 


1.14 


18.6 


5.4 


9.50 


1.16 


21.1 


-0.3 


9.67 


1.18 


23.5 ■■■■-■• 


-3.6 


9.84 


• 


Appendi 


X No. 5 







Temperature 


of Liqu 


id Ammonia 






at 








Various 


Gage 


Pr 


3ssiires 


Gage 


Temperature 








Pressure 


op. 











-28 








.5 


-17 








10 


- 8) 








15 


- 0) 








20 


5) 








25 


-11) 






Usual range of low side 


,30 


17) 








35 


- 21) 








40 


■ 26 








50 


34 








75 


50 








100 


63) 








125 


75) 








150 


84) 






Usual range of high side 


175 


95) 








200 


101) 










Appc 


ndix 


IJo, 


6 



<D 

M 
o 







o 








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H- 








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3 
p- 








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p 






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ro 






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Pressure 
ressure 


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4 






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« 









HP Per Ton for Typical 6x6 Ammonia Compressor 


Cond. Pres. 


Suction Pressure 




10 


' 20 25 


■ 30 


35 




85 


1.30 


.90 .77 


.66 


.56 




105 


1.42 


1.04 .90 


.79 


.68 




125 


1.62 • 


1.18 1.03 ■ 


.91 


.82 




145 


1.75 


1.33 1.17 


1.03 


.93 




165 


1.94 


1.47 1.31. 


1.17 


1.05 




185 


2.12 


1.60 1.44 


1.30 


1.17 




205 


2.29 


1.76 1.57 


1.42 


1.29 




Hi 


^ Per Ton for Typical 9x9 Ammonia Compressor 








Suction Pressure 




10# 


20# 25# 


30# 


35# 




85# 


1.20 


.84 .71 


.61 


.52 




105^ 


1.32 


.97 .84 


.73 


.64 




125# 


1.50 


1.11 .97 


.86 


.77 




; 145# 


1.67 


1.25 1.10 


.98 


.88 




165# 


1.83 


1.39 1.23 


1.11 


1.00 




185# 


2.00 


1.53 1.36 


1.23 


1.11 




205# 


2.17 


1.67 ' 1.50 


1 
1.36 \ 

! 


1.24 






— . 


r^^ppendix No. 8 









REFERENCES Oil COLD STORAGE 

Text Books and Discussions 

of 

Refrigeration Principles and Apparatus 

1. Refrigeration - Ivloyer and Fittz 

2. Principlus of Mechanical Refrigeration - Maclntire 

3. Refrigeration in the Handling, Processing, and Storing 

of Milk and Milk Products - Bowen. Miscellaneous 
Publication 138 US Department of Agriculture. 
For sale by Superintendent of Documents, Washington, 
D. C. — 10 cents. 

4. Instructions for the Operation and liaintenance of Refrigera- 

ting Plants - United States Navy, Bureau of Engineering, 
For Sale by Superintendent of Documents, 'iTashington, 
D. C. — 30 cgnts. 

Handbooks of Specific Information Including Tables of Data 

1» Refrigerating Data Book, Volume 1 - American Society of 
Refrigerating Engineers. 

2, Fan Engineering - A Handbook on air; its movement and distri- 
bution - Buffalo Forgo Company, Buffalo, N. Y. 
(Revised) 1938. 

Discussions and Data 
on 
Cold Storage Operation and Fruit Requirements 

1. i^ef rigerating Data Book, Volume II - iimerican Society of 

Refrigerating Engineers. 

2. Commercial Storage, of Fruits, Vegetables, and Cut Flowers 

Rose, 17right| and V/hitcman. Circular IJo. 278 - 1941 
US Dopartmeni; of Agriculture. For sale by the 
Superintendent of Docuraonts — 10 cents. 

3. The Freezing Temperatures of Some Fruits, Vegetables, and 

Florist Stocks - V/right. Circular No, 447 - 1937. 
Available from Bureau of Plant Industry, YJashington, 
D. C. 

4. A Survey of Fruit Gold Storage Plants in Central Washington 

— Dana. Engineering Bulletin No, 26, Engineering 
Experiment Station, State College of "Yashington, 
Pullman, ITashington, 



-2- 



5. Apple Scald a.nd its Control 

Brooks and Fisher. USDA Farmer's Bulletin 1930. 

6. Soft Scald and Soggy Breakdo■l^^l in Apples 

Brooks and Harlcy. Journal Agr. Res. Volume 49 
No. 1S34. 

7. The Ripening, Storage, and Handling of Apples 

Magnegs, Diohl, Haller and Graham. US Department 
of Agriculture, Bulletin 1406 - 1926. 

8. Apple Harvesting and Storage in British Colunhia 

Britten, Fisher and Calmer. Dominion of Canada 
Department of Agriculture. Publication 724- 1941. 

9. Handling Apples from Tree to Table. 

D. F« Fisher, U» S» Department of Agriculture. 
Circular 659.